At a Glance

Why Get Tested?

When to Get Tested?

When you develop symptoms or signs associated with increased aldosterone production, such as elevated blood pressure, muscle weakness, and low potassium, or low aldosterone production, such as low blood pressure, high potassium, and low sodium

Sample Required?

A blood sample drawn from a vein in your arm or a 24-hour urine sample; sometimes blood from the kidney (renal) or adrenal veins is also collected.

Test Preparation Needed?

For a blood aldosterone and renin measurement, your doctor may ask you to be upright or lying down (e.g., for 15-30 minutes) prior to drawing blood. You may also be instructed to avoid certain foods, beverages, or medications before the test. Follow any instructions you are given.

The Test Sample

What is being tested?

Aldosterone is a hormone that plays an important role in maintaining normal sodium and potassium concentrations in blood and in controlling blood volume and blood pressure. Renin is an enzyme that controls aldosterone production. These tests measure the levels of aldosterone and renin in the blood and/or the level of aldosterone in urine.

Aldosterone is produced by the adrenal glands located at the top of each kidney, in their outer portion (called the adrenal cortex). Aldosterone stimulates the retention of sodium (salt) and the excretion of potassium by the kidneys. Renin is produced by the kidneys and controls the activation of the hormone angiotensin, which stimulates the adrenal glands to produce aldosterone.

The kidneys release renin when there is a drop in blood pressure or a decrease in sodium chloride concentration in the tubules in the kidney. Renin cleaves the blood protein angiotensinogen to form angiotensin I, which is then converted by a second enzyme to angiotensin II. Angiotensin II causes blood vessels to constrict, and it stimulates aldosterone production. Overall, this raises blood pressure and keeps sodium and potassium at normal levels.

A variety of conditions can lead to aldosterone overproduction (hyperaldosteronism, usually just called aldosteronism) or underproduction (hypoaldosteronism). Since renin and aldosterone are so closely related, both substances are often tested together to identify the cause of an abnormal aldosterone.

How is the sample collected for testing?

A blood sample is taken by needle from a vein in the arm to measure blood aldosterone and/or renin. Some doctors prefer 24-hour urine collection for aldosterone since blood aldosterone levels vary throughout the day and are affected by position. In some cases, blood is collected from the renal (for renin) or adrenal (for aldosterone) veins by insertion of a catheter; this is done in the hospital by a radiologist.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

For a blood aldosterone and renin measurement, the doctor may ask you to be upright or lying down for a period of time (e.g., 15-30 minutes) prior to sample collection. You may also be instructed to avoid certain beverages, foods, or medications before the test. Follow any instructions you are given. (For more, see the section "Is there anything else I should know?")

The Test

How is it used?

Aldosterone and renin tests are used to evaluate whether the adrenal glands are producing appropriate amounts of aldosterone and to distinguish between the potential causes of excess or deficiency. Aldosterone may be measured in the blood or in a 24-hour urine sample, which measures the amount of aldosterone removed in the urine in a day. Renin is always measured in blood.

These tests are most useful in testing for primary aldosteronism, also known as Conn syndrome, which causes high blood pressure. If the test is positive, aldosterone production may be further evaluated with stimulation and suppression testing.

Both aldosterone and renin levels are highest in the morning and vary throughout the day. They are affected by the body's position, by stress, and by a variety of prescribed medications.

When is it ordered?

A blood aldosterone test and a renin test are usually ordered together when someone has high blood pressure, especially if the person also has low potassium. Even if potassium is normal, testing may be done if typical medications do not control the high blood pressure or if hypertension develops at an early age. Primary aldosteronism is a potentially curable form of hypertension, so it is important to detect and treat it properly. Aldosterone levels are occasionally ordered, along with other tests, when a doctor suspects that someone has adrenal insufficiency.

Primary aldosteronism (Conn syndrome) is caused by the overproduction of aldosterone by the adrenal glands, usually by a benign tumor of one of the glands. The high aldosterone level increases reabsorption of sodium (salt) and loss of potassium by the kidneys, often resulting in an electrolyte imbalance. Signs and symptoms include high blood pressure, headache, and muscle weakness, espeically if potassium levels are very low. Lower than normal blood potassium (hypokalemia) in someone with hypertension suggests the need to look for aldosteronism. Sometimes, to determine whether only one or both adrenal glands are affected, blood may be taken from both of the adrenal veins and testing is done to determine whether there is a difference in the amount of aldosterone (and sometimes cortisol) produced by each of the adrenal glands.

The most important cause of seconary aldosteronism is narrowing of the blood vessels that supply the kidney, termed renal artery stenosis. This causes high blood pressure due to high renin and aldosterone and may be cured by surgery or angioplasty. Sometimes, to see if only one kidney is affected, a catheter is inserted through the groin and blood is collected directly from the veins draining the kidney (renal vein renin levels); if the value is significantly higher in one side, this indicates where the narrowing of the artery is present.

Low aldosterone (hypoaldosteronism) usually occurs as part of adrenal insufficiency; it causes dehydration, low blood pressure, a low blood sodium level, and a high potassium level. When infants lack an enzyme needed to make cortisol, a condition called congenital adrenal hyperplasia, this can decrease production of aldosterone in some cases.

Is there anything else I should know?

The amount of salt in your diet and medications, such as over-the-counter pain relievers of the non-steroid class, diuretics, beta blockers, steroids, angiotensin-converting enzyme (ACE) inhibitors, and oral contraceptives can affect the test results. Some of these drugs are used to treat high blood pressure. Stress, exercise, and pregnancy can also affect the test results. Coffee, tea or cola can affect the 24-hour urine sample test. Your doctor will tell you if you should change the amount of sodium (salt) you ingest in your diet, your use of diuretics or other medications, or your exercise routine before aldosterone testing.

Licorice may mimic aldosterone properties and should be avoided for at least two weeks before the test because it can decrease aldosterone results. This refers only to the actual products of the licorice plant (hard licorice); most soft licorice and other forms of licorice sold in North America do not actually contain licorice. Check the package label if you are uncertain, or bring a package with you to ask your doctor.

Aldosterone levels become very low with severe illness, so testing should not be done at times when someone is very ill.

1. If my posture is important in the outcome of the results, how can I control it?

2. What is an aldosterone/renin ratio (ARR?)

An aldosterone/renin ratio (ARR) is a screening test to detect primary aldosteronism in high-risk hypertensive individuals. To determine the ratio, blood levels of aldosterone and renin are measured and a calculation is done by dividing the aldosterone result by the renin result. The ARR is considered the most reliable screening for primary aldosteronism, though it is not straightforward to interpret. Anything that could interfere with the test, such as medications, posture, sodium intake, and plasma potassium, needs to be taken into account before the test to avoid false positives or false negatives. Other tests, like suppression tests, are used to confirm the diagnosis after screening.

3. What are aldosterone stimulation and suppression tests?

Suppression tests are used to confirm a diagnosis of primary aldosteronism. In healthy people who are administered a synthetic corticosteroid called fludrocortisone, their plasma aldosterone will be suppressed. The fludrocortisone suppression test requires hospitalization and 4-5 days to complete, so isn't very popular. Saline loading tests, where aldosterone is measured after adding salt to the blood or diet, may be used instead. The dexamethasone suppression test is used in cases where hereditary primary aldosteronism is suspected.

The aldosterone stimulation test, also called ACTH stimulation, tests aldosterone and cortisol to determine if someone has Addison disease, low pituitary function, or a pituitary tumor. A normal result is a cortisol increase after stimulation by ACTH.

4. What is Bartter syndrome?

Bartter syndrome is a group of rare congenital disorders that affect the kidney's ability to reabsorb sodium. People with Bartter syndrome lose too much sodium through the urine. This causes a rise in the level of the hormone aldosterone and makes the kidneys remove too much potassium from the body. The syndrome is therefore associated with high levels of renin and aldosterone in the blood, increased blood pH (alkalosis), and high levels of potassium, calcium, and chloride in the urine.

The syndrome, which is usually diagnosed in early childhood, can be caused by mutations in at least one of five genes, and genetic testing can confirm a diagnosis. There are different types of Bartter syndrome, defined based upon which gene is the cause of the condition.

Signs and symptoms will vary depending on the type of Bartter syndrome someone has. The antenatal form (appears before birth) can be life-threatening. The classical form found in infants and young children usually causes failure to thrive, constipation, muscle cramping and weakness as well as dehydration, increased urine production, and weakened bones.

The condition cannot be cured, but a few treatments are available, such as keeping an affected person's blood potassium above 3.5 mEq/L through a potassium-rich diet or by taking supplements. While, with treatment, prognosis is good, those affected must be careful to maintain fluid and electrolyte balance. Kidney failure is a possible complication of Bartter syndrome. For more information, see The Bartter Site and the sources listed on the Sources page.

Ask a Laboratory Scientist

Form temporarily unavailable

Due to a dramatic increase in the number of questions submitted to the volunteer laboratory scientists who respond to our users, we have had to limit the number of questions that can be submitted each day. Unfortunately, we have reached that limit today and are unable to accept your inquiry now. We understand that your questions are vital to your health and peace of mind, and recommend instead that you speak with your doctor or another healthcare professional. We apologize for this inconvenience.

This was not an easy step for us to take, as the volunteers on the response team are dedicated to the work they do and are often inspired by the help they can provide. We are actively seeking to expand our capability so that we can again accept and answer all user questions. We will accept and respond to the same limited number of questions tomorrow, but expect to resume the service, 24/7, as soon as possible.

Article Sources

NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

(Revised February 2012.) National Adrenal Diseases Foundation. Hypoaldosteronism - The Facts You Need to Know. Available online at http://www.nadf.us/diseases/hyperaldosteronism.htm through http://www.nadf.us. Accessed on Jan. 4, 2012.

The American Association of Endocrine Surgeones. Primary hyperaldosteronism. Available online at http://endocrinediseases.org/adrenal/hyperaldosteronism.shtml through http://endocrinediseases.org. Accessed on Jan. 4, 2013.

(Updated by Nancy J. Rennert, July 26, 2011.) MedlinePlus. Hypoaldersteronism-primary and secondary. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000330.htm through http://www.nlm.nih.gov. Accessed on Jan. 4, 2013.

Bartter syndrome. Genetics Home Reference. Available online at http://ghr.nlm.nih.gov/condition/bartter-syndrome through http://ghr.nlm.nih.gov. Accessed February 2014.

Bartter's Syndrome. National Organization for Rare Disorders. Available online at http://www.rarediseases.org/rare-disease-information/rare-diseases/byID/589/viewAbstract through http://www.rarediseases.org. Accessed February 2014.

(2008 September). The Hormone Foundation's Patient Guide to Detection, Diagnosis, and Treatment of Primary Aldosteronism. The Hormone Foundation [On-line information]. PDF available for download at http://www.hormone.org/Resources/Patient_Guides/upload/detection-diagnosis-and-treatment-of-primary-aldosteronism-122208.pdf through http://www.hormone.org. Accessed July 2009.

Proudly sponsored by ...

Learn more about ...

Get the Mobile App

Follow Us

This article was last reviewed on February 21, 2013. | This article was last modified on May 7, 2014.

The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.

The modified date indicates that one or more changes were made to the article. Such changes may or may not result from a full review of the article, so the two dates may not always agree.